Tank trailers are generally used in the transport industry for the transportation of liquid or solid powdered products. They typically include a large stainless steel tank, made out of a single or of plural internal compartments, and an undercarriage such that they may be pulled on the road by a tractor truck. Tank trailers may be used for transportation of liquid products for example in the food industry (such as milk, syrup or liquid sugar), in the chemical industry (peroxide, phenol, dangerous products) or in the petroleum industry (raw oils). They may also be used for transportation of solid powdered products used in different sectors such as cement, salt or plastic pellets.
The typical tank trailer has several openings that may be found in different locations according to its specific use. Usually, the tank trailer will have an opening at one end to allow for the filling of the tank with the transported product, and one or several openings at the bottom to allow the tank to be emptied. Other than these, one will also find at least one vent, provided for air circulation during the filling and the emptying phases, and one or many manholes, the manholes being generally placed on the top of the tank trailer.
In use, the tank trailer is firstly washed and disinfected before it leaves to be filled with the product to be transported. During the washing process, all of the openings are opened, including manholes on the top of the tank trailer to allow personnel into the tank, for example for inspection purposes. The manholes are usually closed by a flap cover hingedly mounted to the manhole ridge. The vent, as well as the filling and the emptying openings, usually provide an external communication with the inside of the tank only when a specially adapted connector is used. Contrary to the manholes, they do not allow enough room for a person to pass through and access the interior of the tank.
Once the tank has been washed, disinfected and inspected, all the openings are tightly closed and the tank trailer is ready to leave for its first destination in order to be filled. At a relevant facility, the tank trailer is filled with the product. The only openings that are opened during this process are the filling opening and a vent, the others remaining closed. Once filled, the tank trailer is then brought to its delivery destination. The tank is then emptied of its content to deliver the product, the only openings being opened then are the emptying openings and the vent, the others remaining closed. The tank trailer is finally returned to its departure point for washing and sanitising in prevision of another run. One will notice that the manholes never need to be opened during the whole process of transportation.
Independently of the specific product transported into such tank trailers, the industry in general, as well as governments, are now more concerned with the potential danger associated with the tampering of the products inside these tank trailers. The poisoning of a batch of milk, either intentional or accidental, is one example among others of the damage that could result from a tampering of a tank trailer.
A common drawback with prior art tank trailers is that these do not allow locking in place the flap covers closing the manholes in order to eliminate any tampering of the product inside the tank trailer during transportation. The flap covers are easily openable from the outside of the tank trailer, simply by unscrewing the latches. Moreover, these do not provide an operator any means to monitor, from the ground, if any tampering of the product has occurred during transportation.
Therefore, there is a need for a tank trailer that would allow for the locking in place of the manholes as well as for the monitoring of any tampering of the products inside during the transportation process.